The KryptoLok Combo U-lock is like a tough nut: you just can't crack it. Thanks to the 13mm hardened Performance steel shackle that resists cutting and leverage attacks, you get peace of mind while you run into the grocery store or lock up outside the coffee shop. A built-in four-digit resettable combination gives you easy unlocking and locking capabilities--no keys necessary! You can also take advantage of the Transit Flex Frame bracket for plenty of convenient mounting options. The KryptoLok Combo is 4 x 8-inches and has an anti-theft protection offer of $1,250.

Kryptonite's KryptoLok Series 2 Mini-7 may be a little guy, but it packs a big punch thanks to the 13mm hardened Performance steel shackle that resists bolt cutters and leverage attacks. Popular among urban cyclists and messengers, the Mini fits well in a pocket and locks up quickly thanks to the disc-style cylinder and "I" keys, one of which features a high intensity LED for locking and unlocking in the dark. And, it includes the Transit Flex Frame Bracket so you get plenty of mounting options while you ride. The lock measures 3.25 x 7-inches.